Traditionally, to obtain color proof from a plurality of black-and-white halftone images obtained by color separation and dot image conversion by photomechanical processes, the overlay method and the surprint method have been used, which both use photo polymers or diazo compounds to form color images.
The overlay method is advantageous in that it is very simple, it is low cost, and it allows use to prepare a proof simply by overlaying four film sheets of respective colors, subtractive primaries and black; however, it is faulty in that overlaying the film sheets results in surface gloss, leading to a texture different from that of printed matter.
The surprint method, in which colored images are superposed on a single support, is exemplified by the method described in U.S. Pat. Nos. 3,582,327, 3,607,264 and 3,620,726, in which colored images are obtained by toner developing using the adhesion of photopolymerized materials.
Also, Japanese Patent Examined Publication No. 27441/1972 and Japanese Patent O.P.I. Publication No. 501217/1981 disclose a method in which color proof is prepared by forming images by transfer to support using a light sensitive color sheet, followed by exposure and developing, and superposing another color sheet thereon, in repetition. Japanese Patent O.P.I. Publication No. 97140/1984 discloses a method in which colored images obtained by exposing and developing color separation films corresponding to light sensitive color sheets are transferred onto a single support. These methods are advantageous in that coloring materials similar to printing inks can be used as coloring agents for toners and color sheets used to form such images; therefore, the obtained color proof has a tone resembling that of printed matter.
However, these methods are faulty in that much time is required and cost is high because images must be superposed or transferred during the color proof preparation process.
A method using a silver salt color photographic light sensitive material having a white support to prepare color proof, free of these drawbacks, is disclosed in Japanese Patent O.P.I. Publication Nos. 113139/1981 and 104335/1981; however, it is very difficult to reproduce colors of printing inks since the color of each of the yellow, magenta and cyan layers obtained by color separation, exposure and developing of the silver salt color photographic light sensitive material is different from the yellow, magenta or cyan color of printing inks.
In light of this drawback, when using a negative color photographic light sensitive material among the subtractive full-color photographic light sensitive materials as the color proof material, the best tone can be obtained by controlling the wavelength component of exposure light using a filter etc. and properly mixing the yellow, magenta and cyan of the color photographic light sensitive material for a halftone image to approximate the color of each of the dotted yellow, magenta and cyan images to that of printing inks; this method is disclosed in U.S. Pat. No. 4,188,111.
However, it is found by the present inventors that this method is faulty in that when it is used to prepare a color proof, the color of the dots fluctuates increasingly widely as the size of dots decreases.
Among the methods in which a color proof is prepared by exposure and transfer of white-and-black halftone positive images to a positive color photographic light sensitive material, the method in which exposure light wavelength component is controlled is faulty in that it is difficult to obtain a color approximate to that of printing inks by controlling the forming ratio of the yellow, magenta and cyan color in the color photographic light sensitive material, and thus much time is required to control the tone.